From e9be34c9b798141dd6c224cf33934904935c49b2 Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Wed, 7 Jan 2015 19:01:26 +0000 Subject: Complete conversion of s6-ipcserver and s6-tcpserver (4 and 6) to socketbinder + d model. With documentation (!) --- doc/s6-tcpserver4d.html | 112 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 112 insertions(+) create mode 100644 doc/s6-tcpserver4d.html (limited to 'doc/s6-tcpserver4d.html') diff --git a/doc/s6-tcpserver4d.html b/doc/s6-tcpserver4d.html new file mode 100644 index 0000000..018b921 --- /dev/null +++ b/doc/s6-tcpserver4d.html @@ -0,0 +1,112 @@ + + + + + s6-networking: the s6-tcpserver4d program + + + + + + +

+ +

The `s6-tcpserver4d` program

+ +

+s6-tcpserver4d is the serving part of the +s6-tcpserver4 super-server. +It assumes that its stdin is a bound and listening TCP/IPv4 socket, +and it accepts connections from clients connecting to it, +forking a program to handle each connection. +

+ +

Interface

+ +

+     s6-tcpserver4d [ -1 ] [ -v verbosity ] [ -c maxconn ] [ -C localmaxconn ] prog...
+

+ +

s6-tcpserver4d accepts connections from clients to an already +bound and listening TCP socket which is its standard input.
For every TCP connection to this socket, it +forks. The child sets some environment variables, then +executes prog... with stdin reading from the network +socket and stdout writing to it.
Depending on the verbosity level, it logs what it does to stderr.
It runs until killed by a signal. Depending on the received +signal, it may kill its children before exiting.

+ +

Environment variables

+ +

+ For each connection, an instance of prog... is spawned with +the following variables set: +

+ +

PROTO: always set to TCP
TCPREMOTEIP: set to the originating address
TCPREMOTEPORT: set to the originating port
TCPCONNNUM: set to the number of connections originating from +the same IP address

+ +

Options

+ +

-1 : write a newline to stdout, and close stdout, +right before entering the client-accepting loop. +If stdout is suitably redirected, this can be used by monitoring +programs to check when the server is accepting connections. +The s6-notifywhenup +program can be used before the s6-tcpserver +invocation to notify listeners when the server is ready.
-v verbosity : be more or less verbose. +By default, verbosity is 1: print warning messages to stderr. +0 means only print fatal error messages ; 2 means print status and +connection information for every client.
-c maxconn : accept at most +maxconn concurrent connections. Default is 40. It is +impossible to set it higher than 1000.
-C localmaxconn : accept at most +localmaxconn connections from the same IP address. +Default is 40. It is impossible to set it higher than maxconn.

+ +

Signals

+ +

SIGTERM: exit.
SIGHUP: send a SIGTERM and a SIGCONT to all children.
SIGQUIT: send a SIGTERM and a SIGCONT to all children, then exit.
SIGABRT: send a SIGKILL to all children, then exit.

+ +

Notes

+ +

Unlike its ancestor +tcpserver, +s6-tcpserver4d performs just the bare minimum: the point is to have a +very small and very fast process to serve connections with the least +possible overhead. Features such as additional environment variables, +access control and DNS resolution are provided +via the s6-tcpserver-access +program.
s6-tcpserver4d is meant to be execve'd into by a program that gets +the listening socket. That program is normally +s6-tcpserver4-socketbinder, +which creates the socket itself; but it can be a different one if the +socket is to be retrieved by another means, for instance by fd-passing +from a fd-holding daemon (some people call this "socket activation").